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Evidence for Isolation-by-time in the European eel
Maes, G.E.; Pujolar, J.M.; Hellemans, B.; Volckaert, F.A.M.J. (2005). Evidence for Isolation-by-time in the European eel, in: Maes, G.E. Evolutionary consequences of a catadromous life-strategy on the genetic structure of European eel (Anguilla anguilla L.). pp. 117-136
In: Maes, G.E. (2005). Evolutionary consequences of a catadromous life-strategy on the genetic structure of European eel (Anguilla anguilla L.). PhD Thesis. Katholieke Universiteit Leuven. Faculteit Wetenschappen: Leuven. 223 pp., more

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Keywords
    North Atlantic Oscillation; Population genetics; Marine

Authors  Top 
  • Maes, G.E., more
  • Pujolar, J.M.
  • Hellemans, B., more
  • Volckaert, F.A.M.J., more

Abstract
    Life history traits of highly vagile marine species, such as adult reproductive success and larval dispersal, are usually determined by oceanographic and climatic forces. Nevertheless, marine organisms may show restricted dispersal in time and space. Patterns of Isolation-by- Distance (IBD) are commonly observed in marine species. If spawning time is a function of geographical location, temporal and spatial isolation, however, can easily be confounded or misinterpreted. In this study, we aimed at discriminating between various forces shaping the genetic composition of recruiting juveniles of the European eel (Anguilla anguilla L.). By controlling for geographical variation, we assessed temporal variation and tested for Isolation- by- Time (IBT) between spawning cohorts within and between years. Using morphometric traits, as well as 12 polymorphic allozyme and eight variable microsatellite loci, we show that genetic differentiation was low (FST = 0.2 % -0.9%) and significant between cohorts. Regression between genetic and temporal distance, however, was consistent with an inter- annual pattern of Isolation-by- Time. Our data suggest that the population dynamics of the European eel are governed by a double pattern of temporal variance in genetic composition: (1) a broad scale Isolation-by-Time of spawning cohorts, possibly as a consequence of the large migration loop in anguillids or strong variance in annual adult reproductive success; and (2) a small scale variance in reproductive success (genetic patchiness) among monthly spawning cohorts, most likely originating from seasonally oceanic and climatic forces. The consistency of the IBT remains to be verified in spawning or migrating aged adults to confirm its stable or transient nature.

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